There is known SiC (silicon carbide) as a material that is recently expected for use in a high breakdown-voltage power semiconductor device. When SiC is epitaxially grown to obtain an SiC single-crystal thin film, it is necessary to heat a substrate at a high temperature equal to or higher than 1500° C. (“film formation temperature”). To heat the substrate, a lower heater heating the substrate from below and an upper heater heating the substrate from above are provided.
To protect these heaters from corrosive gas such as reactive gas, the corrosive gas is purged from the surroundings of these heaters to make the heaters in an atmosphere of, for example, inert gas such as argon gas. It is particularly necessary to make a space where the lower heater is provided into a perfect atmosphere of inert gas during a film formation process because the lower heater made of carbon is corroded by the corrosive gas such as the reactive gas at a temperature of about 1000° C.
However, the conventional technique has the following problems. During the film formation process, the space where the lower heater is provided is isolated from a space where the film formation process is performed by the substrate mounted on a susceptor, and the corrosive gas is purged from the space of the lower heater and the lower heater is made into the inert gas atmosphere. However, at the time of transporting the substrate into or from the space where the film formation process is performed before or after the film formation process, the space is continuous to the space where the lower heater is provided and the corrosive gas such as the reactive gas enters the space of the lower heater because the substrate is not mounted on the susceptor. Thereafter, when the substrate is heated up to the film formation temperature, the corrosive gas that enters the space corrodes the lower heater. Furthermore, it is necessary to set a temperature at the time of transporting the substrate into or from the space where the film formation process is performed (“transport temperature”) to be equal to or lower than a temperature at which the corrosive gas corrodes the lower heater. It is disadvantageously impossible to improve productivity by increasing the transport temperature at the time of transporting the substrate into or from the space where the film formation process is performed before or after the film formation process.
The present invention has been achieved to solve the conventional problems. An object of the present invention is to provide a film formation apparatus and a film formation method capable of preventing corrosive gas from entering a space where a lower heater is provided and preventing the lower heater from being corroded by the corrosive gas at the time of transporting a substrate into or from a space where a film formation process is performed, and capable of improving productivity by enabling the substrate to be transported in a high temperature atmosphere.